Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$217.89	11.657%	$243.2894	$243.29	$243.30	$243.30
Purchase #2	$81.67	11.756%	$91.2711	$91.27	$91.25	$91.30
Purchase #3	$110.74	10.641%	$122.5238	$122.52	$122.50	$122.50
Purchase #4	$145.69	3.134%	$150.2559	$150.26	$150.25	$150.30
Purchase #5	$179.65	3.199%	$185.397	$185.40	$185.40	$185.40
Purchase #6	$110.61	6.616%	$117.928	$117.93	$117.95	$117.90
Purchase #7	$231.85	4.775%	$242.9208	$242.92	$242.90	$242.90
7 purchase totals =	$1,078.10		$1,153.5860	$1,153.59	$1,153.55	$1,153.60